sedimentary

Limestone

Calcareous sedimentary rock (CaCO3)

Hardness: 3 on the Mohs scale; Color: Gray, white, tan, yellow, or brown; Luster: Earthy to dull; Crystal structure: Microcrystalline or fine-grained calcite; Cleavage: None distinct in rock form (calcite mineral has rhombohedral cleavage); Specific gravity: 2.7 to 2.9

Hardness: 3 on the Mohs scale
Color: Gray, white, tan, yellow, or brown
Luster: Earthy to dull

Identified August 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and compaction of organic remains such as shells, coral, and algal debris, or through the chemical precipitation of calcium carbonate from water, often in shallow marine environments over millions of years.

Uses & applications

Widely used in construction as building stone and crushed stone for road base, as a raw material for manufacturing Portland cement, in agriculture to neutralize acidic soils, and in the production of glass and steel.

Geological facts

Limestone frequently contains well-preserved fossils of ancient marine organisms. Famous structures like the Great Pyramid of Giza and parts of the Empire State Building are constructed using limestone.

Field identification & locations

Easily identified by its characteristic gray or tan color, fine-grained texture, and strong effervescence (fizzing) when a drop of dilute hydrochloric acid or vinegar is applied. Commonly found worldwide in sedimentary basins, quarries, and former seabed regions.